THE  UNIVERSITY 

OF  ILLINOIS 

LIBRARY 


.2. 


1 


NOTICE:  Return  or  renew  all  Library  Materials!  The  Minimum  Fee  for 
each  Lost  Book  is  $50.00. 

The  person  charging  this  material  is  responsible  for 
its  return  to  the  library  from  which  it  was  withdrawn 
on  or  before  the  Latest  Date  stamped  below. 

Theft,  mutilation,  and  underlining  of  books  are  reasons  for  discipli- 
nary action  and  may  result  in  dismissal  from  the  University. 
To  renew  call  Telephone  Center,  333-8400 

UNIVERSITY    OF    ILLINOIS    LIBRARY    AT    URBANA-CHAMPAIGN 


L161—  O-1096 


UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  NO.  249 


CALCIUM  CYANIDE  FOR  CHINCH-BUG 

CONTROL 


IN    COOPERATION    WITH    THE    NATURAL    HISTORY    SURVEY, 
ILLINOIS    DEPARTMENT    OF    REGISTRATION    AND    EDUCATION 

BY  W.  P.  FLINT  AND  W.  V.  BALDUF 


PORTION  OP  A  CALCIUM  CYANIDE  STRIP  USED  AT 
EIGHT  ANGLES  TO  A  CREOSOTE  BARRIER,  SHOWING  DEAD 
CHINCH-BUGS  WHICH  HAVE  ATTEMPTED  TO  CROSS 


UEBANA,  ILLINOIS,  MAY,  1924 


SUMMARY 

Calcium  cyanide  is  a  substance  having  the  appearance  of  slate, 
which  on  exposure  to  moisture  gives  off  hydrocyanic  acid  gas.  In  suffi- 
cient quantities,  it  is  deadly  to  all  forms  of  plant  and  animal  life. 

The  use  of  this  chemical  as  a  means  of  combating  chinch-bugs  was 
first  tried  in  Illinois.  Extensive  tests  were  begun  in  1922  and  were 
continued  thruout  the  season  of  1923.  In  1923  similar  tests  were  made 
in  a  number  of  other  states,  particularly  in  Kansas,  Missouri,  and 
Indiana.  While  it  is  impossible  to  make  definite  recommendations  as 
to  its  use  from  the  results  of  two  years '  work  in  Illinois,  it  is  believed 
that  farmers  will  be  warranted  in  trying  out  some  of  the  methods  de- 
scribed herein. 

The  best  results  from  calcium  cyanide  have  been  obtained  by  using 
either  the  dust  or  the  granules  in  combination  with  creosote  or  coal-tar 
barriers.  Six-inch  strips  of  the  cyanide,  requiring  about  one  ounce 
to  a  strip,  laid  at  right  angles  to  the  barrier  every  two  rods,  have 
under  favorable  conditions  killed  75  to  95  percent  of  the  bugs  as  they 
moved  along  the  line  of  the  barrier.  This  chemical  was  also  very 
effective  when  dusted  along  the  line  of  a  coal-tar  or  creosote  barrier. 

Fair  to  good  results  have  been  obtained  by  dusting  calcium  cyanide 
in  trap  strips  of  crops  sown  between  fields  of  small  grain  and  corn. 
However,  only  one  year's  data  have  been  obtained  with  trap  crops. 

Barriers  of  calcium  cyanide  alone  were  not  so  effective  as  the  other 
methods  and  at  the  same  time  were  more  costly. 


Hydrocyanic  acid  gas  given  off  by  calcium  cyanide  is  very  poisonous, 
and  the  directions  for  handling  given  on  page  84  should  be  carefully  noted. 


CALCIUM  CYANIDE  FOR  CHINCH-BUG 

CONTROL1 


BY  W.  P.  FLINT,  ENTOMOLOGIST,  STATE  NATURAL  HISTORY  SURVEY,  AND 

W.  V.  BALDUF,  ASSISTANT  PROFESSOR  OF  ENTOMOLOGY, 

UNIVERSITY  OF  ILLINOIS 


Calcium  cyanide  was  first  used  in  1922  as  a  means  of  combating 
chinch-bugs  around  the  margins  of  infested  fields  of  small  grain.  Ex- 
periments were  continued  thru  the  season  of  1923,  a  large  number 
of  tests  being  made  during  the  latter  season.  In  the  first  experiments 
this  material  was  used  alone  as  a  barrier.  The  results  showed  it  to  be 
very  effective,  under  some  conditions  killing  every  bug  that  came  in 
contact  with  it,  but  its  use  in  this  way  was  so  costly  as  to  make  it 
unpractical  for  general  use  on  Illinois  farms.  Later  experiments, 
however,  showed  that  it  could  be  used  in  combination  with  creosote 
and  coal-tar  barriers,  thus  greatly  increasing  their  effectiveness  with- 
out increasing  the  cost  to  a  point  where  its  use  would  be  unpractical. 

While  definite  recommendations  of  the  best  way  to  use  calcium 
cyanide  cannot  be  made  from  the  results  of  two  years'  work,  the  re- 
sults here  presented  will  enable  the  Illinois  farmer  to  judge  for  him- 
self the  best  method  of  using  this  material  on  his  farm. 

In  the  Illinois  experiments,  four  methods  of  using  this  chemical 
were  tested  :2 

1.  Laid  in  strips  at  right  angles  to  a  creosote  or  coal-tar  barrier 

2.  Dusted  or  scattered  along  a  creosote  or  other  barrier  at  the 
time  of  day  when  the  bugs  are  most  numerous 

3.  Dusted  over  strips  of  trap  crops  sown  between  infested  small 
grain  and  corn 

4.  Alone  as  a  barrier  around  the  margins  of  the  infested  field 

1  NOTE. — Calcium  cyanide  ia  a  cheap  form  of  rather  low-grade  cyanide.  It  has 
about  half  the  strength  of  the  sodium  cyanide  generally  used  in  hydrocyanic  acid 
gas  fumigation  of  fruit  trees,  greenhouses,  and  flour  mills.  When  this  chemical  is 
«xposed  to  air  containing  the  usual  amount  of  moisture,  or  is  applied  to  damp  soil, 
the  poisonous  hydrocyanic  acid  gas  is  liberated  in  sufficient  quantities  to  kill  in- 
sects or  other  animals  exposed  to  it,  for  varying  periods  of  time. 

3  Some  tests  were  also  made  to  determine  the  effect  of  calcium  cyanide  dust 
when  applied  directly  to  corn.  While  it  proved  very  effective  in  killing  the  chinch- 
bugs  clustered  on  the  plants,  it  cannot  be  used  for  chinch-bug  control  because  it 
nearly  always  penetrates  the  curl  of  the  leaves  and  causes  the  death  of  the  plant 
or  a  severe  burning.  A  2-percent  nicotine  dust  used  in  this  way  is  just  as  effective 
as  calcium  cyanide  dust  in  killing  the  bugs,  is  cheaper,  and  does  not  injure  the  corn. 

73 


I 

74  BULLETIN  249  [May, 

Three  forms  of  calcium  cyanide  were  tried  out:  (1)  flakes,  which 
have  the  appearance  of  finely  broken  slate,  the  separate  flakes  being 
from  one-fourth  to  one-half  inch  across  and  about  one  sixty-fourth 
inch  thick;  (2)  granules,  having  the  same  form  as  flakes  but  being 
much  finer,  the  larger  particles  being  only  about  one-eighth  inch 
across;  (3)  dust,  the  material  ground  to  a  fine  powder. 


USED  IN  STRIPS  AT  RIGHT  ANGLES  TO  A  CREOSOTE 
OR  COAL-TAR  BARRIER 

In  1923  the  method  of  control  proving  the  most  practical  was  the 
use  of  calcium  cyanide  strips  laid  at  right  angles  to  the  creosote  or 
coal-tar  barrier.  These  strips  are  made  by  putting  down  one  to  one 
and  one-half  ounces  of  cyanide  in  each  strip,  laid  from  three  to  five 
inches  wide  and  from  six  to  eight  inches  long.  These  strips  are  made 
at  right  angles  to  the  barrier,  touching  the  creosote  on  the  side  next 
the  stubble  field.  They  should  be  spaced  every  two  rods  along  the 
line.  In  the  corners  of  the  field,  where  the  bugs  usually  gather  in 
greatest  number,  it  may  be  necessary  to  lay  the  strips  closer  together. 

^^^^Creo5ote^barrier^6in.wide^^^^^^ 
^^^roSs"^^™!^^^"  "' " 

-4>  <y  ty> 

'H  Co) 


C  CO  'O 

5  «o~'^ 

??  >^c  s 

w  ^%  o  •—  w  ,_ 

£P"  _  «O  ~  „  O- 

_'C  £     .£  £"£ 

j  *2  _;  53  (TV  t3  ft 

5  8**  u 

FIG.  1. — DIAGRAM  SHOWING  THE  METHOD  OF  LAYING  CAL- 
CIUM CYANIDE  STRIPS  AT  EIGHT  ANGLES  TO  A  CREOSOTE  OR 
COAL-TAR  BARRIER 

Care  should  be  taken  that  the  strips  actually  connect  with 
the  barrier.  The  slope  toward  the  barrier  should  be  gradual  so 
that  the  cyanide  will  not  roll  down  and  away  from  the  creosote 
or  coal  tar. 

Chinch-bugs  attempting  to  leave  the  fields  of  small  grain  and  en- 
countering barriers  of  creosote  or  coal  tar  are  repelled  by  the  odor  of 
these  substances.  In  the  case  of  coal  tar,  they  are  held  back  by  the 
stickiness  of  the  material  as  well.  Hence  they  turn  and  start  along 
the  stubble  side  of  the  barrier,  seeking  an  opening  thru  which  they 
can  escape  into  fields  of  corn  or  to  other  food  plants.  Half -grown 
young,  or  nymphs,  travel  along  the  barriers  at  the  rate  of  five  to  six 


1984]  CALCIUM  CYANIDE  FOR  CHINCH-BUG  CONTROL  75 

feet  a  minute,  and  are  almost  sure  to  encounter  a  cyanide  strip  in  five 
minutes  or  less  after  they  get  to  the  barrier. 

Tests  of  this  method  extended  over  a  period  of  two  months  in  1922 
and  a  somewhat  longer  period  in  1923,  and  were  made  under  varying 
weather  and  soil  conditions.  Under  some  conditions  pure  dust  was 
found  to  be  the  most  effective  form  to  use.  When  the  soil  is  wet,  the 
granules  are  better  than  the  dust  because  they  do  not  lose  their 
strength  so  rapidly.  The  flakes  also  give  better  results  than  the  dust 
when  the  ground  is  wet,  but  they  are  not  very  effective  when  the  soil 
is  dry  or  when  the  wind  blows  briskly.  In  general,  granular  calcium 
cyanide  is  the  most  practical  form. 

Care  should  be  taken  that  the  strips  actually  connect  with  the 
creosote  barrier.  The  slope  toward  the  barrier  should  be  sufficiently 
gradual  so  that  the  cyanide  will  not  roll  down  and  away  from  the 
creosote. 

A  sprinkling  can  from  which  the  sprinkling  cap  has  been  removed 
is  a  convenient  vessel  to  use  for  pouring  the  cyanide.  After  a  little 
practice  one  is  able  to  quickly  put  down  strips  of  approximately  one 
ounce  each  at  the  intervals  specified. 

STRIPS  ARE  EFFECTIVE  FOR  A  LIMITED  TIME 

When  the  soil  is  dry  and  the  wind  strong,  most  bugs  can  cross  the 
cyanide  strips  without  being  killed.  Under  more  favorable  conditions, 
however,  the  strips  are  effective  up  to  five  or  more  hours.  Usually  on 
warm  bright  days,  the  heavy  movement  of  chinch-bugs  starts  between 
2 :30  and  3 :30  in  the  afternoon,  the  bugs  gathering  along  the  barrier 
in  greatest  numbers  between  3 :30  and  5 :30.  The  most  effective  kill 
can  therefore  be  made  by  laying  the  strips  between  3:00  arid  4:00 
o'clock  in  the  afternoon.  Except  when  the  soil  is  dry  and  the  wind 
high,  strips  laid  at  this  time  remain  effective  for  the  rest  of  the  after- 
noon and  may  be  counted  on  to  kill  75  to  95  percent  of  all  bugs  reach- 
ing the  barrier. 

If  the  amount  of  cyanide  in  the  strips  is  doubled,  and  the  flake  or 
granular  form  is  used,  some  bugs  will  be  killed  the  following  forenoon, 
if  no  rain  has  fallen  during  the  night ;  but  the  strips  will  not  remain 
effective  during  the  entire  day.  Since  the  -bugs  seldom  migrate  in 
large  numbers  in  the  morning,  the  kill  is  not  sufficiently  increased  to 
warrant  the  added  expense  of  using  these  larger  amounts  of  cyanide. 

Occasionally  on  cloudy  days  there  is  a  considerable  movement  of 
chinch-bugs  all  day.  In  such  weather  the  cyanide  should  be  applied 
between  9 :00  and  10 :00  o  'clock  in  the  forenoon,  and  another  applica- 
tion made  in  the  afternoon  if  necessary.  Becaiise  the  creosote  or  coal- 
tar  barrier  holds  the  chinch-bugs  in  the  field,  it  is  very  seldom  neces- 
sary to  make  more  than  one  application  a  day,  even  during  cloudy 
weather. 


76  BULLETIN  249  [May, 

EXPENSE  or  COMBINED  BARRIER 

The  total  cost  for  a  quarter  of  a  mile  of  creosote  or  coal-tar  barrier 
and  cyanide  strips  along  it  is  about  $21  for  the  migration  period.  This 
is  figuring  cyanide  at  20  cents  a  pound  delivered  at  the  local  shipping 
point  and  the  cost  of  creosote  or  coal  tar  at  $5  to  $7  for  the  season. 
This  will  not  be  thought  too  expensive  to  be  practical  if  one  remembers 
that  he  is  not  only  stopping  the  bugs  but  is  actually  killing  the  ma- 
jority of  them.  Post  holes  are  unnecessary  where  calcium  cyanide 
cross-strips  are  used,  for  the  cyanide  kills  more  bugs  than  are  usually 
caught  in  the  post  holes.  The  saving  of  the  labor  of  digging  the  post 
holes  helps  pay  the  expense  of  the  cyanide. 

USED  ALONG  A  CREOSOTE  OR  COAL-TAR  BARRIER 

The  second  method  of  using  calcium  cyanide  in  combination  with  a 
creosote  or  coal-tar  barrier  is  to  distribute  small  amounts  along  the 
barrier,  on  the  side  of  the  field  of  small  grain,  instead  of  in  strips  at 
right  angles  to  the  barrier.  To  be  effective,  the  calcium  cyanide  should 
be  laid  down  each  day  when  the  bugs  are  gathering  in  greatest  num- 
bers. For  this  method,  the  cyanide  dust  has  been  found  most  practical. 

The  expense  of  this  treatment  is  somewhat  higher  than  that  of  the 
right-angle  strips,  but  on  windy  days,  when  the  soil  is  very  dry,  it  is 
more  effective  and  more  convenient  than  the  strips.  The  cost  of  the 
calcium  cyanide  is  from  $1  to  $1.50  a  day  for  each  quarter-mile  of 
barrier. 

This  method  has  the  disadvantage  of  requiring  a  close  watching  of 
the  barrier,  for  in  order  to  get  a  maximum  kill  the  dust  must  be  ap- 
plied when  the  bugs  are  present  along  the  barrier  in  greatest  numbers. 
While  this  is  usually  about  4 :30  in  the  afternoon,  the  time  may  vary  a 
great  deal  with  weather  conditions.  One  application  a  day  is  neces- 
sary. This  kills  all  the  bugs  massed  against  the  barrier  at  the  time 
and  those  coming  into  the  dusted  area  for  ten  to  thirty  minutes  there- 
after. The  duration  of  the  kill  depends  upon  weather  conditions. 

How  TO  APPLY  THE  DUST 

The  calcium  cyanide  dust  may  be  applied  with  a  blower  duster  or  a 
homemade  shaker.  The  duster  is  of  the  type  commonly  used  for  dust- 
ing truck  crops  or  small  fields  of  cotton ;  it  costs  from  $10  to  $25,  and 
is  apparently  no  more  effective  for  this  purpose  than  a  homemade 
shaker.  A  convenient  and  efficient  shaker  can  be  made  in  the  fol- 
lowing way : 

Obtain  a  gallon  or  half-gallon  tin  pail  with  a  tight-fitting  lid.  (The 
lid  is  important  in  confining  the  fluffy  and  poisonous  dust. )  Make  an 


1924] 


CALCIUM  CYANIDE  FOR  CHINCH-BUG  CONTROL, 


77 


extension  bail  by  nailing  narrow  strips  of  wood  eighteen  inches  long 
to  opposite  sides  of  the  pail  and  joining  them  above  with  a  piece  of 
broom  stick.  (The  extension  bail  enables  the  operator  to  walk  erect 
and  at  the  same  time  to  distribute  the  material  close  to  the  ground  so 
that  it  will  not  be  carried  away  by  the  wind. )  From  the  outside  of  the 
pail,  punch  four  to  six  holes  per  square  inch  in  the  bottom,  using 
an  eight-penny  nail. 


FIG.  2. — HOMEMADE  SHAKER  FOR  APPLY- 
ING CALCIUM  CYANIDE  DUST 

This  shaker  must  have  a  tight-fitting  lid 
to  prevent  the  escape  of  the  poisonous  dust. 

Fill  the  pail  two-thirds  full  of  dust  and  walk  along  the  barrier, 
forcing  the  material  out  by  a  jiggling  motion.  The  dust  may  be  ap- 
plied as  rapidly  as  one  can  walk  down  the  side  of  the  field.  Approxi- 
mately one  pound  of  the  dust  to  thirteen  rods  of  barrier  was  found  to 
be  effective. 


A  creosote  barrier  is  made  by  throwing  up  a  ridge  of  earth  around 
the  infested  field  of  small  grain  and  applying  creosote  along  the  brow 
of  the  ridge  on  the  side  toward  the  field  of  small  grain.  The  furrow 
should  be  turned  away  from  the  grain  field. 

The  creosote  is  applied  with  a  galvanized  or  tin  bucket  having  a 
six-penny  nail  punch  in  the  side  near  the  bottom.  The  stream  of 
creosote  should  be  directed  against  the  brow  of  the  ridge  on  the  side 
toward  the  field  of  small  grain,  as  above  stated,  so  that  the  bugs  in  at- 
tempting to  leave  the  field  will  crawl  up  to  it.  The  creosote  must  be 
renewed  once  a  day  during  the  first  week,  and  should  always  be  ap- 


78  BULLETIN  249  [May, 

plied  on  the  same  line.     After  the  first  week  an  application  every 
other  day  is  usually  sufficient. 

The  application  should  be  made  usually  about  1 :00  o  'clock  in  the 
afternoon,  before  the  bugs  have  gathered  along  the  line.    It  is  the  odor 


of   earth 
Creosobe  line 


Wheat  stubble 


FIG.  3  —  CONSTRUCTION  OF  A  CREOSOTE  BARRIER  ,11813)  ALONE 

Where  calcium  cyanide  strips  are  to  be  used  with  the 
creosote  or  coal-tar  barrier,  the  slope  of  the  ridge  should  be  more 
gradual  than  shown  here. 

of  the  creosote  that  keeps  them  from  crossing  the  barrier  ;  consequently 
if  the  line  is  renewed  when  the  bugs  are  massed  against  it,  many  be- 
come confused  by  the  strong  smell  of  creosote  in  the  air  and  run  over 
the  barrier. 

A  barrel  of  creosote,  on  an  average,  is  required  to  maintain  a  half- 
mile  of  barrier  during  the  period  the  bugs  are  leaving  the  wheat 
stubble.  The  creosote  should  preferably  be  of  a  grade  with  a  high 
napthalene  content. 

A  line  of  ground  limestone  is  sometimes  spread  along  the  brow  of 
the  ridge  and  the  creosote  applied  on  this  line.  Limestone  retains  the 
odor  of  creosote  better  than  does  the  soil  and  so  increases  somewhat  the 
effectiveness  of  the  barrier. 


DIRECTIONS  FOR  MAKING  A  COAL-TAR  BARRIER 

Coal  tar  may  be  used  as  a  barrier  in  much  the  same  manner  as 
creosote,  but  the  ground  on  which  it  is  poured  should  be  nearly  level 
and  should  be  compacted  as  firmly  as  possible,  and  a  larger  quantity 
of  coal  tar  than  of  creosote  will  need  to  be  used. 

It  must  be  borne  in  mind  that  the  effectiveness  of  the  coal-tar  bar- 
rier depends  largely  on  its  sticky  character.  It  will  have  to  be  re- 
newed more  frequently  than  the  creosote,  and  since  about  twice  as 
much  coal  tar  as  creosote  is  required,  this  kind  of  barrier  usually  costs 
more  than  one  of  creosote. 


W24~\  CALCIUM  CYANIDE  FOR  CHINCH-BUG  CONTROL  79 

Coal  tar  for  this  work  may  be  obtained  from  gas  plants  in  any  of 
the  larger  cities.  There  is  a  wide  difference  in  the  grades  that  may  be 
obtained  from  different  plants.  Coal  tar  which  contains  practically  aJJ 
the  creosote  is  much  more  effective  for  barriers  than  that  from  which 
a  part  of  the  creosote  compounds  have  been  distilled. 


USED  ON  TRAP  CROPS 

Many  attempts  have  been  made  to  control  chinch-bug  migrations 
by  stopping  the  bugs  in  narrow  trap  strips  of  their  favorite  food 
plants  sown  between  the  small  grain  fields  and  the  fields  of  corn  or 
other  crops  to  be  protected.  There  seemed  to  be  a  possibility  of  using 
calcium  cyanide  with  such  trap  crops  by  applying  it  when  the  bugs 
were  gathered  in  the  trap  strips,  and  in  1922  some  experiments  were 
made  with  this  method.  No  special  trap  crops  had  been  sown,  but 
strips  of  wild  grasses  growing  between  the  small  grain  and  the  corn 
were  dusted  with  calcium  cyanide  and  a  fair  kill  of  bugs  was  obtained. 

In  1923  this  trap  crop  and  cyanide  combination  was  tested  more 
thoroly.  Strips  of  oats,  millet,  Sudan  grass,  and  corn  were  sown  be- 
tween heavily  infested  fields  of  small  grain  and  of  corn.  These  strips 
were  treated  with  flake,  granular,  and  dust  calcium  cyanide  at  varying 
intervals  and  at  varying  rates  of  application.  Altho  these  tests  ex- 
tended over  the  migration  period  of  one  season,  the  results  were  not 
conclusive.  Apparently  this  method  is  not  so  effective  as  the  creosote 
barrier  with  the  cyanide  laid  along  it  or  in  strips  at  right  angles  to  it. 
However,  the  method  may  be  worth  trying  under  some  conditions. 

Of  the  trap  crops  used  on  the  University  Farm  in  1923,  Sudan 
grass  was  decidedly  the  most  effective.  It  is  very  attractive  to  chinch- 
bugs  and  withstands  a  considerable  amount  of  feeding  by  them  before 
it  is  killed.  It  is  vigorous,  and  hence  can  also  endure  the  bruising 
by  teams  and  machinery  which  occurs  in  cultivating  the  corn.  It 
is  not  easily  killed  by  heavy  applications  of  calcium  cyanide,  and  the 
sheaths  of  the  leaves  fit  so  tightly  to  the  stems  that  chinch-bugs  can- 
not get  between  them  and  the  stalk  and  thus  be  protected  from  the 
fumes  of  the  gas.  The  rows  of  Sudan  grass  should  be  sown  thickly 
and  close  together  so  that  a  bug  can  scarcely  pass  thru  the  strip  with- 
out encountering  a  plant. 

Some  tests  with  rye  made  during  the  latter  part  of  the  summer 
showed  that  this  plant  is  apparently  second  to  Sudan  grass  as  a  trap 
crop.  It  is  hardier  than  oats  and  nearly  as  attractive  to  the  bugs  as 
Sudan. 

Millet  and  oats  were  found  to  be  quite  susceptible  to  cyanide. 

Corn,  even  when  seeded  with  a  drill,  formed  a  very  poor  trap  crop, 
many  bugs  going  thru  the  strip  and  into  the  field  of  corn  beyond.  The 


80 


BULLETIN  249 


[May, 


corn  was  also  very  susceptible  to  the  effects  of  the  cyanide  dust,  one 
or  two  dustings  killing  the  plants. 

From  the  results  of  this  work  thus  far,  the  following  statements 
can  be  made : 

To  be  in  the  best  condition  for  stopping  the  bugs,  a  trap  crop 
should  form  a  thick,  close  covering  over  the  ground  and  should  not  be 
more  than  six  inches  high  at  the  time  the  chinch-bugs  migrate.  For 
this  reason,  the  trap  strip  should  not  be  sown  when  the  corn  is  planted, 


FIG.  4. — DUSTING  A  TRAP-CROP  STRIP 
WITH  A  BLOWER  DUSTER 

The  trap  crop  shown  here  is  Sudan 
grass,  which  is  somewhat  higher  than  it 
should  be  for  this  purpose.  To  get  the 
best  results,  the  trap  crop  should  not  be 
more  than  six  inches  high. 

unless  rye  is  used.  Sudan  grass  should  be  planted  one  to  two  weeks 
after  the  corn  is  in  the  ground.  The  time  of  planting  depends,  how- 
ever, on  the  expected  time  of  small  grain  harvest  and  not  on  the  size 
of  the  corn.  The  trap  strips  should  be  three  and  one-half  feet  or 
more  wide,  and  to  insure  a  thick  growth,  they  should  be  sown  with 
about  one  and  one-half  times  the  usual  amount  of  seed. 


1934]  CALCIUM  CYANIDE  FOE  CHINCH-BUG  CONTROL  81 

In  this  method  of  using  calcium  cyanide,  dust  was  found  to  be 
the  most  desirable  form. 

The  dust  may  be  applied  to  the  trap  crops  by  means  of  a  duster  or 
a  homemade  shaker.  The  shaker  is  not  so  good  for  this  purpose  as  the 
regular  blower  duster;  however,  it  gives  a  very  fair  distribution  of 
the  dust  providing  the  trap  strip  is  not  more  than  six  inches  high. 
The  trap  strips  must  be  dusted  once  a  day  when  a  heavy  migration  of 
the  bugs  is  taking  place.  The  dusting  is  most  effective  when  done  be- 
tween 4 :30  and  5 :30  in  the  afternoon. 

Judging  from  experiments  made  thus  far  at  this  Station,  calcium 
cyanide  dust  must  be  applied  at  the  rate  of  about  one  pound  for  each 
two  and  one-half  rods  of  trap  strip  three  feet  wide.  This  is  at  the 
rate  of  one  pound  of  dust  to  each  one  hundred  and  twenty  square  feet. 
Under  favorable  conditions,  such  an  application  kills  from  80  to  95 
percent  of  the  bugs  gathered  in  the  strip,  but  when  the  wind  is  strong 
and  the  crop  dry,  the  results  are  not  nearly  so  good.  The  amount  of 
kill  seems  to  depend  in  a  general  way  on  the  amount  of  moisture 
present  in  the  trap  crop,  the  velocity  of  the  wind,  the  height  and 
density  of  the  trap  strip,  and  perhaps  some  other  factors. 

Calcium  cyanide  granules  may  be  used  in  treating  these  trap  strips 
and  can  be  applied  by  hand  at  the  same  rate  as  the  dust.  Where  the 
trap  crop  is  wet  with  rain  or  dew,  the  granules  are  seemingly  fully  as 
effective  as  the  dust,  but  on  dry  soil  and  plants  they  do  not  result  in  so 
large  a  kill. 

The  above  statements  are  not  to  be  taken  as  definite  recommenda- 
tions for  the  use  of  the  trap  strip  and  calcium  cyanide  combination 
for  chinch-bug  control.  It  will  be  necessary  to  carry  on  experiments 
for  one  more  season  at  least  before  definite  recommendations  can  be 
made. 


USED  ALONE  AS  A  BARRIER 

More  than  three  hundred  separate  tests  have  been  made  in  Illinois 
to  determine  the  practicability  of  the  flake,  granular,  and  dust  forms 
of  cyanide  used  alone  as  chinch-bug  barriers.  Under  favorable  con- 
ditions it  was  found  that  nearly  all  the  bugs  attempting  to  leave  a  field 
of  small  grain  on  foot  may  be  killed  along  such  a  barrier,  if  a  sufficient 
amount  of  the  cyanide  is  applied.  Under  less  favorable  conditions, 
however,  the  results  were  extremely  variable.  In  some  kinds  of 
weather,  one-half  to  one-fourth  pound  of  cyanide  per  rod  of  barrier 
killed  all  bugs  attempting  to  cross  it  during  a  period  of  three  to  five 
hours.  With  other  weather  conditions,  the  same  amount  permitted 
50  percent  of  the  bugs  to  cross  in  fifteen  to  thirty  minutes  after  it  was 
applied. 


82 


BULLETIN  249 


[May, 


In  these  tests,  the  calcium  cyanide  was  used  in  various  positions 
and  at  various  rates.  It  was  used  on  soil  from  which  all  vegetation 
had  been  removed,  on  the  top  of  the  plow  furrow  ridge,  in  strips  in 
the  stubble  (which  protected  it  somewhat  from  the  action  of  the  wind 
and  sun),  and  in  the  bottom  of  a  plowed  furrow  or  trench  dug  around 
the  margins  of  the  field.  Only  when  used  in  a  furrow  or  trench  did  it 
give  promise  of  having  practical  value  as  a  barrier,  under  the  condi- 
tions encountered.  Used  in  this  way  the  gas  is  somewhat  confined, 
and  if  the  soil  is  damp  and  little  or  no  wind  blows  down  the  furrow, 
the  gas  accumulates  sufficiently  to  kill  most  of  the  bugs  over  a  con- 
siderable period  of  time.  If  the  soil  is  dry,  and  the  wind  is  strong 
along  the  furrow,  the  kill  is  small,  even  when  the  cyanide  is  used  in 
the  bottom  of  the  furrow. 

In  Table  1  are  shown  the  results  of  144  tests  of  cyanide  used  in  the 
furrow ;  they  give  an  idea  of  the  diverse  effects  of  the  chemical  under 
different  weather  conditions  encountered. 

TABLE  1. — EFFECTIVENESS  OF  VARIOUS  AMOUNTS  AND  FORMS  OF  CALCIUM  CYANIDE 
USED  ALONE  IN  THE  FURROW  AS  CHINCH-BUG  BARRIERS 


Form 

Amount  used 
on  each  rod 
of  barrier 

Number 
of 

tests 

Average  time 
during  which  90 
percent  of  bugs 
were  killed 

Variation  in  time 
during  which  90 
percent  of  bugs 
were  killed 

Flakes  
Flakes  

Ibs. 
4 
2 

3 
3 

hrs. 

m 

%1A 

hrs. 
3    to  20 
1    to  17 

Flakes  .  .  . 
Flakes.  .  . 
Flakes.  .  . 
Flakes  .  .  . 

1 

H 

X 
K 

18 
15 

17 
4 

4 

m 

ix 

H 

Yz  to  15 
J^to    VA 
M  to    4 
J€to    11A 

Granular  . 
Granular  . 
Granular  . 
Granular  . 

2 
1 
H 

X 

3 
15 
12 
13 

4% 

314 
1H 

IH 

1    to  10 
lAio!7 
1A  to    5 
1A  to    6 

Dust,  pure 

4 

1 

5 

Dust,  pure 

2 

1 

5 

Dust,  pure 
Dust,  pure 
Dust,  pure 
Dust,  pure 

1 
« 

1A 

% 

13 
11 
10 
5 

3^ 
VA 
1*4 
g 

1    to    5 

y2  to  e 

1A  to    3 
1A  to    1 

On  still,  damp  days,  one-half  to  one-fourth  pound  of  flakes,  gran- 
ules, or  dust  of  calcium  cyanide  to  a  rod  makes  an  ideal  barrier  in  a 
furrow  five  to  seven  inches  deep.  The  cyanide  should  be  applied  on 
the  furrow  bottom  at  the  point  farthest  from  the  grain  stubble.  The 
bugs  are  then  forced  to  climb  up  the  steep  side  of  the  furrow  directly 
above  the  cyanide,  and  as  a  result,  their  movements  are  slowed  up. 
Thus  they  are  exposed  to  the  gas  for  a  longer  time  than  when  the 
cyanide  is  placed  in  the  middle  of  the  furrow  or  along  the  side  down 
which  they  tumble  in  leaving  the  stubble. 


1984]  CALCIUM  CYANIDE  FOR  CHINCH-BUG  CONTROL  83 

As  may  be  seen  from  Table  1,  where  one-fourth  to  one-half  pound 
of  calcium  cyanide  per  rod  was  used,  it  was  in  some  cases  effective  for 
as  long  as  six  hours.  Under  such  conditions,  the  cyanide  applied  at 
1 :00  o  'clock  could  be  depended  upon  to  kill  90  percent  of  all  the  bugs 


„  ..  side  of  furrow 

/ 
/  /Point  where  cyanide 

7     should  be  applied 
Small  (grain  stubble 


FIG.  5. — MOST  EFFECTIVE  CONSTRUCTION  OF  A  CALCIUM 
CYANIDE  BARRIER 

The  straight  side  of  the  furrow  should  always  be  toward  the 
corn,  and  the  calcium  cyanide  should  be  laid  at  the  base  on  this 
side,  as  shown  above.  If  a  trench  is  dug,  the  cyanide  should  be 
applied  at  the  same  point. 

attempting  to  leave  the  field  during  the  afternoon.  In  other  cases,  the 
same  amounts  of  cyanide  applied  in  the  same  way  and  in  the  same 
places  were  effective  only  for  fifteen  to  thirty  minutes;  that  is,  it 
would  be  necessary  to  make  three  to  five  applications  to  maintain 
an  effective  barrier  during  an  afternoon. 

Used  at  the  rate  of  one-fourth  of  a  pound  per  rod,  an  amount  of 
calcium  cyanide  sufficient  to  maintain  a  barrier  a  quarter  of  a  mile 
long  would  cost  $4  a  day.  This  figure  is  based  on  a  price  of  20  cents 
per  pound  for  the  cyanide  delivered  at  the  farmer's  shipping  point. 
For  a  fourteen-day  migration  period,  material  for  a  quarter-mile  of 
barrier  would  cost  $56.  The  experiments  show  that  on  a  number  of 
days  two  or  three  times  this  amount  of  cyanide  would  have  to  be  used ; 
therefore  one  can  hardly  count  on  maintaining  an  effective  barrier  for 
the  season  at  less  than  $70  to  $75  for  each  quarter-mile.  This  is 
nearly  three  times  the  expense  of  killing  the  bugs  with  a  combination 
of  creosote  and  calcium  cyanide,  or  nearly  ten  times  the  cost  of  main- 
taining a  creosote  barrier. 

Because  of  the  great  variation  in  the  results  of  experiments  made  to 
date,  definite  recommendations  for  the  use  of  cyanide  alone  as  a  bar- 
rier cannot  be  made  at  this  time.  During  the  past  season  work  sim- 
ilar to  that  done  in  Illinois  has  been  carried  on  in  Kansas,  Missouri, 
and  Indiana.  Rather  favorable  results  have  been  obtained  with  the 
barriers  in  Missouri.  The  results  in  Kansas  and  Indiana  compare  very 
closely  with  those  obtained  in  Illinois.  Judging  from  all  the  tests 
made,  it  may  be  said  that  a  chinch-bug  barrier  can  be  maintained  by 
the  use  of  calcium  cyanide  alone,  but  that  the  expense  of  maintaining 


84  BULLETIN  249 

such  a  barrier  is  so  great  as  to  make  it  unpractical  except  for  the  pro- 
tection of  a  very  valuable  crop,  such  as  seed  corn. 

Of  the  different  forms  of  calcium  cyanide  tried  for  barrier  work, 
the  dust  has,  on  the  whole,  given  the  best  results,  mainly  because  of  its 
physical  character.  The  small  particles  afford  unstable  footing  for  the 
bugs  when  they  attempt  to  cross  the  line.  This  retards  their  move- 
ment, and  they  are  exposed  to  the  gas  for  a  considerably  longer  time 
than  when  trying  to  cross  a  line  of  flakes  or  granules.  These  coarser 
forms  of  the  cyanide  evolve  the  gas  more  slowly  than  the  dust,  and 
do  not  greatly  retard  the  movements  of  the  bugs.  On  the  other  hand, 
when  the  soil  is  very  damp,  the  dust  gives  off  its  gas  so  rapidly  that 
it  soon  weakens  and  does  not  continue  to  kill  over  a  very  long  period. 
Under  such  conditions  the  coarser  forms  of  cyanide  are  to  be  pre- 
ferred. 


HOW  TO  HANDLE  CALCIUM  CYANIDE 

Caution  is  necessary  in  handling  calcium  cyanide.  The  gas  given 
off  from  this  material  is  one  of  the  most  deadly  known.  However, 
the  calcium  cyanide  used  for  chinch-bug  control  is  comparatively 
weak  in  hydrocyanic  acid  gas,  and  if  one  is  careful  not  to  get  his  head 
directly  over  the  container,  or  to  breathe  in  the  dust  or  the  fumes 
of  the  freshly  opened  cans,  there  is  little  danger.  There  is  appar- 
ently very  little  hazard  in  handling  the  material  in  the  open  air  if 
one  keeps  on  the  windward  side  of  the  container.  The  writers  have 
worked  with  it  for  the  past  two  seasons,  and  have  purposely  tested 
the  effects  upon  themselves  in  a  number  of  different  ways.  Occa- 
sionally when  enough  of  the  dust  was  breathed  into  the  nostrils,  par- 
ticularly when  the  distributing  utensils  were  being  filled  from  the 
larger  cans  in  which  the  material  was  shipped,  a  severe  headache  was 
caused.  This  discomfort  disappeared  after  an  hour  or  two  in  the 
open  air;  but  one  must  be  careful  at  all  times.  Cyanide  should  not 
be  left  in  the  field  or  around  buildings  where  children  or  farm  animals 
might  possibly  reach  it.  Fowls  that  have  access  to  it  sometimes  pick 
up  the  flakes  or  granules,  with  fatal  results. 


